Conventionally, a can container commonly used for containing soft drink, alcoholic beverages and even foods and the like comprises a cylindrical can body having a bottom and a disk-like can lid for closing an open end of the can body. Recently, the can lids used in the above type of can container have mostly employed a certain type of tab, or what is called a stay-on tab, in which the tab is placed in a partially coupled state with the can body even after opening of the can lid. This stay-on type tab is attached to the can lid via a rivet arranged integrally in a substantially central region of a can lid body.
In such fastening of the tab with use of the rivet, if the used rivet has a poor fastening force, the tab could be easily turned around the rivet in parallel with the can lid body, or substantially along the horizontal plane. This is a phenomenon referred to as “tab turning”. The tab turning may occur in a manufacturing process and/or a packaging process and may also possibly occur when a user pulls up the tab at a location offset from a central region of a lift-up section of the tab.
The event of the tab turning can alter the physical relationship between an opening region (tear-strip) and a tab tip end (tab nose). Since the tab nose defines a section serving to apply a force to the opening region during the opening process, any change in the above physical relationship could prohibit a predetermined pressing force from being obtained. In addition, if there is occurrence of severe tab turning, the tab nose may be shifted away from the opening region, bringing about obstacles in opening and ending up with a problem of the opening ability.
In order to avoid such problems, many different means have been used to prevent the tab turning. There is one such related art technique by way of example that has employed a non-circular rivet so as to prevent the tab turning. In the related art technique, the rivet is configured to have an elliptical shape in cross section, so that the tab would not turn even if such a great force that could turn the tab were applied to the tab. In this technique, the conventional design can be still employed for other aspects than the rivet geometry (see following related art 1). There are other related art techniques as disclosed, including one type of can lid that includes a protrusion referred to as a tab dimple disposed in the can lid and another type of can lid that is manufactured by using a favorably modified pressing degree of a rivet (see following related art 2).
FIG. 6 shows a related art technique, in which a finger inserting recess 58 is formed in an area of the can lid body adjacent to a pull-up section 59a of a tab 59. The finger inserting recess 58 defines a recess to facilitate hooking action by a user in hooking his/her finger on the pull-up section 59a of the tab 59.
[Related Art 1]                Japanese Patent Public Disclosure No. 2002-179062        
[Related Art 2]                Japanese Patent Public Disclosure No. 2004-196349        